Press ENTER or SPACE to edit a slice's details, or click on a slice to edit the topmost slice that's visible. (Some slices, like containers, are also excluded from being clicked on because they're always invisible). The topmost slice under the mouse is outlined, and all slices under the mouse are highlighted in the slice listing, with the topmost in a different colour.

Hold the SHIFT key and use the arrow keys to reorder the slice in the slice list. Moving it to the top of the list makes it draw first. Moving it to the bottom of the list makes it draw last, over the top of the other slices.

Hold Shift and press the left and right arrow keys to change the parentage of a slice. If a slice is indented that means it is a child of the slice right above it in the menu.

Child slices are grouped together with their parent, and they move as a group.

While holding Ctrl you can press up and down to move to the previous and next siblings of a slice; and press left and right to select the parent and the first child.

Right click to select the top-most visible slice. Hold CTRL to rightclick on invisible slices including containers, panels, etc.

Even when Pick isn't the current tool, you can still select slices by Right-clicking, or with ALT+up/down, and also with Ctrl+arrow keys (see above).

Tools:

Pick (press P): the default mode (pressing ESC goes back to Pick). Up/down keys just change the selected slice in the list of slices.

Click anywhere to get a popup menu listing all the slices at that point, including invisible ones. (You can also right-click to select the top-most slice as usual.) They are indented to show which slices are descendents of each other (rather than direct children like the main menu). The selected slice is drawn on top of the collection (if it's visible).
Many keys such as V visibility, Delete, Copy/Paste, and right-drag-panning still work in this submenu.

Move (press M): move a slice with arrow keys and mouse drags.

Resize (press R): resize a slice with arrow keys and mouse drags.

Right-Dragging with the mouse always lets you pan (move around) the slice collection.

Pan (press N or F6): lets you also pan the view of the collection with the arrow keys in addition to Right-Dragging. Panning doesn't modify the collection, it is only for help while editing.

Press a tool's shortcut key again to deselect it.


Extra functions:

(Tip: Most of the following keys are also listed when you select a slice and press F8 for the Settings menu.)

Press V to toggle a slice visible/invisible. This doesn't work on the children of Select slices. Invisible slices have a different colour in the menu.

Press H or - to hide (and again to show) the children of a slice in the editor menu. That is, collapse part of the slice tree.

Or press Left/Right to show/hide the slice children. Press them repeatedly to show or hide even more of the slice tree.

Press Z to reset a slice's position: to position 0,0, aligned and anchored to top-left corner, and not filling parent.

Press F to focus on the selected slice, shifting (panning) the view of the slice tree to put it near the screen center.

Press Delete if you want to remove the selected slice. Select the root slice or "<- Collection # ->" to delete the whole collection.

Press Ctrl+C to copy a slice and its children. Press Ctrl+V to paste a copied slice before the current one. Press Ctrl+C while no slice is selected to copy all slices in the collection.

Press F2 to export (save) your slice collection to a file.

Press F3 (in Custom only) to import a slice collection (asks whether to overwrite the collection you are currently working on, or to open a seperate slice editor for it).

Press CTRL+F to edit the currently selected slice and its children in a full-screen subeditor, hiding the rest of the collection.

Press F4 to switch between hiding the menu background, hiding the menu (so you can see the slice collection unobstructed), hiding the slices, or showing both.

Press F5 to toggle whether the root slice is shown. For a slice collection, the root slice is by default a container set to fill its parent (which results in it filling the whole screen in the editor). "load slice collection" returns a handle to this root slice. You can freely change any of the properties of the root slice or even turn it into something else if you don't want an extra container.
NOTE: if you add no children to the root slice, it won't be saved!

Press F7 to toggle whether outline boxes are drawn around the currently selected slice and the one under the mouse.

Press F8 to open the Slice Editor Settings menu, where you can access most of these functions without having to remember the hotkey for each.

Press Ctrl/Shift+F3 to toggle between 8-bit and 24-bit color mode. This affects transparency/blending in the slice editor only.

Press Ctrl/Shift+F5 to switch between the different blending algorithms (8-bit color mode only). You can also change this from a slice's blending settings.